| (57) A method of recovering dihydric phenol, particularly bisphenol-A, from compositions
containing the reaction residue of bisphenol-A units which method comprises:
a. granulating a bisphenol-A containing polymer;
b. treating the particles with an alcohol, or any other organic swelling solvent miscible
with water and easily distilled off from an aqueous solution, preferably a C1-C10, alcohol for a time sufficient to swell the particles;
c. contacting the swelled particles with a ammoniacal solution at a temperature of
at least about 25°C depending on the swelling solvent employed in order to selectively
sever the ester bonds of the bisphenol-A residue units;
d. separating the liquid phase from the solid phase;
e. distilling ammonia and swelling solvent from the liquid phase of d. above, thus
obtaining an essentially aqueous solution with dissolved urea and partially precipitated
bisphenol-A;
f. adding sufficient water to the residue of e. above to precipitate bisphenol-A thereby
forming a liquid and solid phase;
g. recovering the solid phase of bisphenol-A; and
h. drying the bisphenol-A.
Since urea is soluble in water, urea goes into solution in step f. above. The urea
is, therefore, recoverable, as well, which can be used as such or broken down into
its component parts such as carbon dioxide and ammonia which ammonia can also be reused
in this ammonical process.
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